To solve recent global environmental issues, the shift from gasoline vehicles to hybrid electric vehicles and electric vehicles has been promoted and the use of electric bicycles has been increased. A variety of energy storage devices such as lithium ion secondary batteries are widely used in these applications. For this reason, energy storage devices having a higher output have been demanded.
To meet this demand, an energy storage device that attains a higher output by use of non-graphitizable carbon as a negative electrode active material has been proposed in the related art (see Patent Literature 1: WO2005/098998). The increased output in the energy storage device is attained by use of a non-graphitizable carbon having an average particle size D50 of 1 to 20 μm (preferably 4 to 15 μm) as a negative electrode active material to be formed into a negative electrode.